Storytelling and Narrative - Fundamentals of Game Design - page 171

Game events—either player events or in-game events generated by the core
mechanics (such as an action taken by an AI-driven NPC) —determine which
branch the story will take. Player events that influence the direction of the story
fall into two categories: efforts to overcome a challenge or decisions that the story
asks the player to make. Branch points connected with player decisions have one
branch for each option that you offer to the player. Typically, branch points associ-
ated with challenges have only two branches leading on from the branch point,
one for success and one for failure, though you can also create different numbers of
branches for different degrees of success if you want to. We'll consider the emo-
tional consequences of branches based on challenges versus those based on choices
in the later section “Endings.”
IMMEDIATE, DEFERRED, AND CUMULATIVE INFLUENCE
If an event in the game causes the plot to branch right away, that event has an
immediate influence on the story. This is the most common kind of branch and the
easiest to implement. The player makes an irrevocable decision—which road to
take, for example—and the story promptly reflects his choice.
However, sometimes the player can make a decision early in the game that influ-
ences a branch point much later, in which case that decision has deferred influence,
or he can make a whole series of decisions throughout the game that cumulatively
affect a branch point, such that his actions and decisions, taken together, have
cumulative influence.
If you use deferred or cumulative influence, you must make it clear to the player
what the possible consequences of his decisions will be. It's unfair to give the player
a choice early in the game without warning that this choice will have long-term
repercussions, and then change the direction of the story hours or days later based
on that choice. Furthermore, if he wants to change his mind, he has to reload the
game all the way back at the point where he first made the choice, choose differ-
ently, and then play all the way through the game again. (That's assuming he still
has a save point there to reload from.) And he can only do this at all if he realizes
how his decisions affected the current branch, which may not be obvious.
For example, if you allow a player to choose right at the beginning of a role-playing
game whether he will play as a healer character or a fighter character, you should
tell him that such an important choice will have significant deferred consequences
throughout the game.
Many role-playing games use cumulative influence to build up a sort of reputation
for the player. The game keeps track of the player's behavior over time, and if the
player consistently performs evil deeds, the NPCs in the game begin to treat him as
an evil character. Again, you should warn the player that his cumulative behavior
will have consequences later in the game.